Yale University researchers also examined the obesity issue, combing through 88 studies.
They found that people tend to eat more calories on days when they drink a lot of sugar-sweetened drinks, and that soda drinkers tend to be heavier than people who don't drink soft drinks.
The researchers hypothesized that the body does not easily recognize calories derived from beverages, so people end up eating more. But the Yale study wasn't designed to prove that.
As for diet sodas, nutrition researcher David L. Katz, MD, who directs the Yale Prevention Research Center, told WebMD in November 2010 that the research as a whole suggests sugar substitutes and other non-nutritive food substitutes have little impact on weight. “For every study that shows there could be a benefit or harm, there’s another that shows no ‘there’ there,” Katz says.